按日期分組的實體框架總和時間

Question

我有以下代碼，我得到了錯誤

無法將類型“字符串”隱式轉換為“長”

錯誤來自(i => i.TotalHours) 。

我究竟做錯了什么？ 或者我需要改變什么？

桌子

視圖模型

private void CalculateTime()
{
    var result = context.TimeSheets.GroupBy(o => o.StartDate)
                        .Select(g => new { StartDate = g.Key, total = g.Sum(i => i.TotalHours) });

    foreach (var group in result)
    {
        Console.WriteLine("StartDate = {0} TotalHours={1}", group.StartDate, group.total);
    }
}

Class：

public class TimeSheet
{
    [Key]
    public int ID { get; set; }

    [StringLength(255)]
    public string MachineID { get; set; }

    public DateTime StartDate { get; set; }

    public DateTime StartTime { get; set; }

    public DateTime EndDate { get; set; }

    public DateTime EndTime { get; set; }

    [StringLength(225)]
    public string WorkDescription { get; set; }

    [StringLength(225)]
    public string ClientName { get; set; }

    [StringLength(225)]
    public string UserName { get; set; }

    public string TotalHours { get; set; }
}

Answer 1

根據您的錯誤，我相信您需要將TotalHours類型更改為long或進行類型轉換，請嘗試： (long)Convert.ToDouble(i.TotalHours)

var result = context.TimeSheets.GroupBy(o => o.StartDate)
                    .Select(g => new { StartDate = g.Key, total = g.Sum(i => (long)Convert.ToDouble(i.TotalHours)) });